docs: def add_duration(self, key, value):
          """Add a duration for the specified key
  
          :param str key: The value name
          :param float value: The value
  
          .. versionadded:: 3.19.0
  
          """
          if key not in self.durations:
              self.durations[key] = []
          self.durations[key].append(value)